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Chelates in dog foods

  • September 2016
DOI:10.13140/RG.2.2.28134.63045
Authors:
Anton Beynen
Anton Beynen
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Abstract

Chelates in dog foods Some dog foods feature chelated trace elements such as zinc, iron, copper, manganese and selenium. These elements are bound to compounds with multiple carbon atoms and called organic trace elements. The word chelate has become trendy in the marketplace and works as blanket term. Technically, chelate structures consist of a ring of atoms with the trace element as link, and so form a specific class of organically bound trace elements. Chelated trace elements in petfood are purported to outwork inorganic sources that contain no or only one carbon atom. It is often claimed that chelates are taken up by intestinal cells more efficiently, have prominent regulatory and catalytic activity in the body's metabolism and support the immune system. A few dog foods highlight added organic zinc as booster of a soft and shiny hair coat. Trace elements are essential nutrients. Most commercially prepared canine foods are supplemented with trace elements and contain higher amounts than dogs' requirements. As additives, either inorganic or organic elements can be used. If a certain organic element is absorbed by the small intestine more efficiently, a smaller element quantity meets the intended absorbable dose. Nevertheless, the use of chelates is more expensive, but this may not discourage application as marketing tool. Downregulation of absorption protects the body against excess of trace elements. The intestinal uptake routes of chelates might bypass the body's security mechanism. Little is known about the nature of degradation products of intactly absorbed chelates. Research data in the public domain cannot substantiate chelate-mediated health advantages in dogs. All in all, organic trace elements do not appear to be superior to inorganic sources. Petfood and trace elements Fear for deficiencies and process simplification explain why commercial petfoods are supplemented with liberal amounts of trace elements. Food-specific supplementation is no easy task. For each element it involves determining the background concentration in the diet, estimating absorbability, setting the supply of the target animal and judging the need and form of supplementation. The conceptual relationship between intake of an individual trace element and health status of an animal spans amounts ranging from deficiency to adequacy to toxicity. Dietary supplementation appears pointless when supply is in the adequacy range. There is no evidence that higher intakes improve canine health while homeostatic regulation inhibits absorption and/or stimulates excretion. Below the adequacy range, supplementation promotes health. Smaller quantities are needed for trace elements with higher absorbability. Efficiency of absorption
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Creature Companion 2016; July: 52, 54.
Anton C. Beynen
Chelates in dog foods
Some dog foods feature chelated trace elements such as zinc, iron, copper, manganese and
selenium. These elements are bound to compounds with multiple carbon atoms and called organic
trace elements. The word chelate has become trendy in the marketplace and works as blanket
term. Technically, chelate structures consist of a ring of atoms with the trace element as link, and
so form a specific class of organically bound trace elements.
Chelated trace elements in petfood are purported to outwork inorganic sources that contain no or
only one carbon atom. It is often claimed that chelates are taken up by intestinal cells more
efficiently, have prominent regulatory and catalytic activity in the body’s metabolism and support
the immune system. A few dog foods highlight added organic zinc as booster of a soft and shiny
hair coat.
Trace elements are essential nutrients. Most commercially prepared canine foods are
supplemented with trace elements and contain higher amounts than dogs’ requirements. As
additives, either inorganic or organic elements can be used. If a certain organic element is
absorbed by the small intestine more efficiently, a smaller element quantity meets the intended
absorbable dose. Nevertheless, the use of chelates is more expensive, but this may not discourage
application as marketing tool.
Downregulation of absorption protects the body against excess of trace elements. The intestinal
uptake routes of chelates might bypass the body’s security mechanism. Little is known about the
nature of degradation products of intactly absorbed chelates. Research data in the public domain
cannot substantiate chelate-mediated health advantages in dogs. All in all, organic trace elements
do not appear to be superior to inorganic sources.
Petfood and trace elements
Fear for deficiencies and process simplification explain why commercial petfoods are supplemented
with liberal amounts of trace elements. Food-specific supplementation is no easy task. For each
element it involves determining the background concentration in the diet, estimating absorbability,
setting the supply of the target animal and judging the need and form of supplementation.
The conceptual relationship between intake of an individual trace element and health status of an
animal spans amounts ranging from deficiency to adequacy to toxicity. Dietary supplementation
appears pointless when supply is in the adequacy range. There is no evidence that higher intakes
improve canine health while homeostatic regulation inhibits absorption and/or stimulates excretion.
Below the adequacy range, supplementation promotes health. Smaller quantities are needed for
trace elements with higher absorbability.
Efficiency of absorption
For dogs, there only is published information on the absorption of organic zinc, but it was not
quantified. Upon ingestion of equal amounts of zinc in gelatin capsules as either zinc oxide or zinc
propionate, the latter induced higher plasma zinc concentrations, indicating more efficient
absorption (1). Similar results were obtained when a zinc-amino acid chelate (2) or zinc proteinate
(3) was compared with zinc oxide.
The zinc content of a dry food without added zinc was almost doubled by incorporating zinc oxide or
zinc-amino acid chelate (4). The chelate lowered fecal zinc excretion. Increasing dietary calcium
raised fecal zinc output for the food with zinc oxide, but not for that with zinc chelate (4). When a
solution with zinc sulfate or zinc methionylglycinate was administered orally after each meal of
extruded food, the apparent absorption percentage of total ingested zinc was 30 and 37% (5).
Theoretical considerations
Organic versus inorganic zinc has enhanced absorbability in dogs. Organic trace elements may be
more soluble in the intestinal content, which increases availability for absorption. They might easily
pass the mucus and unstirred water layer on the intestinal wall. Possibly, chelates cross the mucosa
through passive transport or carrier systems for their organic moiety. These routes would bypass
homeostatic downregulation of absorption which is undesired from a teleological point of view.
Trace elements that are absorbed as organic molecule must be released prior to utilization as co-
factor of enzymes and for other cellular functions. The delivery might be associated with the
formation of undesired substances. High intakes of either sodium selenite or selenomethionine
induced similar hepatic accumulation of selenium in dogs (6), most likely encased in selenocysteine
or selenomethionine along with selenocysteine.
Organic zinc and hair quality
Dogs fed a complete food containing organic instead of inorganic zinc grew more hair of higher zinc
content (4, 5, 7, 8). Methionine (4, 5, 7) or a hydroxyl analogue (8) was a constituent of the organic
zinc source, but the amount added seems negligible. The increased zinc retention in hair was
attributed to higher availability of zinc from the organic sources. However, the observation may
reflect zinc accumulation caused by uncontrolled absorption and disturbed zinc homeostasis.
Organic zinc induced smoother and less fragmented hair as based on electron microscopy (5, 9).
Veterinarians blinded to treatment modality assigned statistically, significantly higher brightness
scores to the hair of supplemented dogs (8). The mean scores were 2.4 and 2.1 on a 1-3 scale which
questions practical significance.
Substantiation of claims
There are no research data in the public domain showing that trace elements in either inorganic or
organic form improve canine health at intakes higher than the recommended allowances. Petfood
manufacturers wishing to use chelates for health claims must rely on the suppliers’ data.
Literature
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2. Lowe JA, Wiseman J, Cole DJA. Absorption and retention of zinc when administered as an amino-
acid chelate in the dog. J Nutr 1994; 124: 2572S-2574S.
3. Wedekind KJ, Lowry SR. Are organic zinc sources efficacious in puppies? J Nutr 1998; 128: 2593S-
2595S.
4. Lowe JA, Wiseman J, Cole DJA. Zinc source influences zinc retention in hair and hair growth in the
dog. J Nutr 1994; 124: 2575S-2576S.
5. Jamikorn U, Preedapattarapong T. Comparative effects of zinc methionylglycinate and zinc sulfate
on hair coat characteristics and zinc concentration in plasma, hair, and stool of dogs. Thai J Vet Med
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levels of dietary inorganic and organic selenium. J Anim Sci 2012; 90: 2549-2555.
7. Lowe JA, Wiseman J. A comparison of the bioavailability of three dietary zinc sources using four
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8. Trevizan L, Fischer MM, Rodenbush CR, Labres RV, Kessler AM. Effects of diets containing organic
and inorganic zinc sources on hair characteristics, zinc concentration in blood and hair, and the
immune response of dogs. Acta Sci Vet 2013; 41: 1154.
9. Kuhlman G, Rompala RE. The influence of dietary sources of zinc, copper and manganese on
canine reproductive performance and hair mineral content. J Nutr 1998; 128: 2603S-2605S.
Beynen AC, 2019. Yeast in petfood
Article
Full-text available
  • Mar 2019
Yeast in petfood Many dog and cat foods declare a yeast ingredient, most commonly brewer's dried yeast, but also yeast extract, yeast cell walls, selenium yeast or yeast culture. Brewer's yeast is a by-product from the brewing of beer or ale. Extracts and cell walls are yeast parts. Selenium yeast is grown in nutrient mixtures enriched with the trace element. Yeast culture is yeast and its growth medium. Until the 1950s, whole dried yeast served as source of B-vitamins in experimental dog foods with highly purified ingredients. By using that kind of foods, black-tongue disease in dogs was found to respond to consumption of brewer's yeast (1), which led to the identification of vitamin B3. Yeast is lauded as B-vitamin powerhouse, but is as such needless for current petfoods that are effectively and profitably supplemented with pure B vitamins. Similar reasoning holds for selenium yeast (2). Brewer's yeast in petfood is rarely linked to health claims. Nutritional yeast supplements may promise flea control, healthy skin and coat, but do so without evidence. About 1% of brewer's yeast is often added to dry food for palatability, which requires securing for each application. MOS (mannan-oligosaccharides) from yeast cell walls is touted for gut and immune health, but dog studies are unsupportive (3). Purified yeast beta-glucans can stimulate immune responses, albeit without known impact on pets' health maintenance (4). Yeasts constitute a wide variety of single-celled organisms. Many are safe and useful such as the species employed in baking and production of beverage and fuel alcohol. Moderate yeast amounts in petfood seem harmless to dogs and cats. Curiously, one petfood brand carries "no added yeast" as label claim (5). As specific yeast species can cause skin infections in dogs, anti-yeast foods are being proposed, but their efficacy is unsubstantiated. Composition Brewer's yeast (Saccharomyces cerevisiae) is derived from drying the slurry that remains after beer and ale fermentation. Due to different practices of breweries, the composition varies, but can be put at 41% protein, 3% fat, 0.5% crude fiber, 6% ash, 5% moisture and 44.5% nitrogen-free extract (6). Dried, whole yeast contains about 10% of both mannan-oligosaccharides (3) and beta-(1,3)/(1,6)-glucans (4). Digestibility Dogs received an extruded reference diet as such or with brewer's yeast in 85:15 mixing ratio (7). Apparent total tract digestibilities of crude protein for the reference and yeast-containing diet were 84.7 and 86.2% of intake (n=7/diet). With the difference method, the digestibility of protein in brewer's yeast was calculated to be 88.8%. Two forms of sugarcane yeast had protein digestibilities of 63.0 and 74.7% (7). Protein digestibility for other types of yeast extracts was 72.4% in dogs (8) and 78.6% in cats (9).
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Effects of Diets Containing Organic and Inorganic Zinc Sources on Hair Characteristics, Zinc Concentration in Blood and Hair, and the Immune Response of Dogs
Article
Full-text available
  • Oct 2013
Background: There are two commercial forms of zinc, organic and inorganic, and its form may influence absorption and utilization by the animals. The inorganic form dissociates to Zn2+ in the gastrointestinal tract and can interact with other substances that the animal cannot absorb. The interest in using organic minerals has increased because of the reported potential of higher bioavailability compared to inorganic sources. In dogs, little research has been done concerning the bioavailability of organic and inorganic mineral sources. This study compared the effects of diets containing organic and inorganic zinc on hair characteristics, zinc concentration in blood and hair, and the influence of organic minerals on the immune response of dogs. Materials, Methods & Results: Eighteen healthy adult dogs of different breeds (Labrador, German Shepherd, Malinois Shepherd, and Rottweiler) were separated into two groups of nine animals per treatment and fed diets for 30 days. Two diets were used: an inorganic mineral source diet (IMSD) and an organic mineral source diet (OMSD). Four parameters were evaluated (days -14, 0, 10, 20, 30) to determine the hair characteristics: brightness, texture, looseness, and greasiness. On days 0 and 30, two blood samples were taken and two hair samples were collected to measure zinc concentrations. On the 10th day of the trial period, the animals received an injection of 4 mL of a 10% solution of sheep red blood cells (SRBC) subcutaneously as a stimulus to assess the humoral response. Blood samples were taken prior to injection as well as on days 10 and 20 post-injection for antibody titer. All dogs consumed adequate amount of the diets and body weight did not change during the experiment. The daily dry matter, energy, and zinc consumption did not differ between groups. The zinc concentration in the blood remained stable throughout the experiment in animals fed the OMSD but decreased significantly in the animals fed the IMSD (P = 0.0145). The zinc concentration in hair increased (P = 0.0075) in dogs fed the OMSD, while the dogs fed the IMSD had no difference. The consumption of the OMSD resulted in higher brightness in the hair of the face, muzzle, armpit, back, abdomen, and tail compared with the IMSD. The animals fed the chelated mineral-supplemented diet also showed better texture in hair of the abdomen (P = 0.0327), chest (P = 0.0335), and tail (P = 0.0291). The parameters looseness and greasiness showed no significant differences. No differences were observed in the production of antibodies against SRBC between groups; however, the antibody concentration was maintained throughout the experiment in the animals supplemented with OMSD, in contrast to the animals supplemented with IMSD, which reduced their antibody concentration. Discussion: There is controversy in the literature regarding the benefits of organic over inorganic zinc source. This may be due to two factors: the time of zinc supplementation, and the levels of zinc included in the diets, which varies in each experiment. In the present study, both criteria were adequate for the responses evaluated and the results suggest that organic zinc is suitable for supplementation into the commercial dog foods and could enhance the hair characteristics of adult dogs. Moreover, the improvement in immune status, although subtle, must be taken into account. It should be noted that the diets were formulated with high levels of minerals, especially calcium, which increases the possibility of interactions and competition in the absorptive process, increasing the challenge and impairing absorption of divalent minerals.
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Selenium status in adult cats and dogs fed high levels of dietary inorganic and organic selenium
Article
Full-text available
Cats (Felis catus) maintain greater blood Se concentrations compared with dogs (Canis familiaris) and, unlike dogs, show no signs of chronic Se toxicity (selenosis) when fed dietary organic Se (selenomethionine) concentrations of 10 μg/g DM. This study investigated the response of cats and dogs to high dietary concentrations of sodium selenite and organic Se to determine differences in metabolism between both species. In 2 consecutive studies, 18 adult cats and 18 adult dogs of with equal numbers of each sex were fed a control diet (0.6 μg Se/g DM) or the control diet supplemented to 8 to 10 μg Se/g DM from Na(2)SeO(3) or organic Se for 3 wk. All animals were fed the control diet 1 mo before the start of the study and blood samples were taken on d 0 and 21. The Se balance was assessed during the final week and a liver biopsy was obtained on the final day of the study. Measurements included plasma Se concentrations, plasma glutathione peroxidise (GPx) activities, plasma Se clearance, Se intake, and urinary Se excretion. No clinical signs of selenosis were observed in the cats or dogs, and apart from Se clearance, form of Se had no effect on any of the measurements. Apparent fecal Se absorption was greater in the dogs fed both forms of Se, while greater plasma Se concentrations were observed in the cats on both the control and supplemented diet (P = 0.034). Cats fed the supplemented diets had lower hepatic Se concentrations (P < 0.001) and excreted more Se in urine (P < 0.001) compared with dogs. Furthermore, cats fed the Na(2)SeO(3) supplement had greater Se clearance rates than dogs (P < 0.001). There was no effect of species on plasma GPx activity. We conclude that cats can tolerate greater dietary Se concentrations as they are more efficient at excreting excess Se in the urine and storing less Se in the liver.
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Comparative Effects of Zinc Methionylglycinate and Zinc Sulfate on Hair Coat Characteristics and Zinc Concentration in Plasma, Hair, and Stool of Dogs
Article
There are two form of Zn supplement used in commercial dog foods, organic and inorganic forms. These forms can influence Zn absorption and utilization of the animals. The goal of the current study was to evaluate the effects of zinc methionylglycinate (ZnMG) compared to zinc sulfate (ZnSO4) supplementations in commercial dog foods on haircoat characteristics, and Zn concentration in plasma, hair, and stool of the dogs. Eight mature female beagles were randomly divided into two groups of four dogs each. A Cross-over design was used for this study. The treatments composed of 120 ppm Zn supplement of either ZnMG or ZnSO4. A commercial dry dog food formulated with no Zn supplementation (only from raw materials) was used as the basal diet. Each experimental period lasted 5 wk with the first 2 wk as adaptation period and the last 3 wk as time of Zn supplement. Blood samples were collected for the measurement of serum ALP activity and plasma Zn concentration. Hair was shaved and used to analyze for Zn deposition. Haircoat characteristics were determined under electron microscope. The dogs supplemented with ZnMG had greater hair growth rate, level of Zn deposition in hair, serum ALP activity, amount of Zn absorption (p<0.05), and plasma Zn concentration (p<0.10). The hair of the dogs received ZnMG supplement appeared to be smoother and lesser fragmented than the dogs received ZnSO4 supplement. In conclusion, the organic Zn as ZnMG was found to be the form that could enhance the haircoat characteristics and suitable for supplementation into the commercial dry dog foods.
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Effects of diets containing organic and inorganic zinc sources on hair characteristics, zinc concentration in blood and hair, and the immune response of dogs
  • Jan 2013
  • 1154
  • L Trevizan
  • M M Fischer
  • C R Rodenbush
  • R V Labres
  • A M Kessler
Trevizan L, Fischer MM, Rodenbush CR, Labres RV, Kessler AM. Effects of diets containing organic and inorganic zinc sources on hair characteristics, zinc concentration in blood and hair, and the immune response of dogs. Acta Sci Vet 2013; 41: 1154.